Antenna for 144 MHz
Want to offer to the readers of the magazine design of the antenna, obtained as a result of experiments with the framework antennas. The proposed antenna may be of interest to radio Amateurs operating on УSW ranges and are not able to manufacture or install the antenna with a long traverse.
This antenna is a modified zigzag design of the antenna described K. Kharchenko , proven when receiving TV signals. General view of the antenna represented in Fig.1.
The antenna is designed to operate in the Amateur range of 2 m. It has small size, does not require special material costs and careful tuning. At the same time, the antenna has a pronounced directional properties, quite a wide band, in good agreement with feeder and has a high gain.
In this example, the antenna radiates or receives a vertically polarized wave. For horizontal polarization antenna must be deployed along the axis 90°, and preferably change the shape of the elements on the diamond. The antenna elements made in the form of an equilateral triangular frames made of aluminum wire with a diameter of 5 mm. you Can use a rod or tube made of copper, brass or bi-metal diameter of from 4 to 9 mm. In this case the structure will be heavier.
All parties to the framework is the same. The length of a side of the triangle at the reflector is 740 mm, the vibrator - 700 mm, with the Director - 665 mm. the Total perimeter of the reflector -4400 mm vibrator - 4200 mm, Director - 4000 mm permissible deviation in dimensions 10...20 mm. the distance between the reflector-vibrator - 480 mm, vibrator-Director - 280 mm.
Frame made from a single pigtail.
At the geometric center of the reflector and Director (point "A" in Fig.2 and 3) conductors are connected in circuit with the help of rivets.
If possible, the connection it is desirable to solder to provide a reliable galvanic contact. The vibrator of the conductors in the center posted on 10...20 mm (Fig.4).
In this place the vibrator is connected to the feeder. Core of the wire connected to the bottom with respect to the ground pin of the vibrator (point "a"), and braid of the cable to the upper output (point "b").
Frame antenna mounted on platforms from the insulator by using a strap. Pad size 100x120 mm, made of PCB thickness of 5 mm, but you can use another insulating material (acrylic, ebonite, etc.).
Using a small corner site with frames are attached to the traverse. Carrier made from wooden bar section of 30x40 mm and length 1 m. To the mast the antenna is mounted in the manner specified in the drawing (Fig.5).
As feeder, you can use coaxial cable with a characteristic impedance of 50 or 75 Ohms.
In this case, to assess the degree of matching of the antenna with feeder was used УSW-reflectometer factory manufacturing. The CWS in the feeder at frequencies 145...145.7 MHz to 1:1,1.
The gain on the voltage at the receiving end compared with the antenna of the GP amounted to U1/U2=1:5,18.
Very good results have shown the antenna when receiving TV signals on UHF. Designed for 30-channel antenna covers the entire UHF television-land.
1. Kharchenko K. Zigzag antenna. Radio, 1962, N11;1977, N6.
Author: S. Machuga (US5MGZ); Publication: N. Bolshakov, rf.atnn.ru